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  3. question 19 10 points suppose you work for a large...

Question: question 19 10 points suppose you work for a large...

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Question 19 (10 points) Suppose you work for a large electrical designs firm that designs electrical control systems for industrial manufacturing sites. Assume your design requirements include specifying short circuit and ground fault protection for motor circuits. These device specifications should comply with the National Electric Code. Your design, started in early 1991, involved the selection of a non-time delay fuse for a three-phase, 230V, 50 hp, 115A (its name plate values) induction motor for a molded rubber parts plant. The code book says that the full rated current for this motor is to be 130A. The book also states that for this type of non-time delay fuse the current should not be more than 300% of rated. However, you find that commercially available uses come only in increments of 50A near that value. You choose the 400A fuses since the code implies that it is permissible (and is a widely accepted practice) to round up to this higher value. Your design was not implemented as the project was tentatively canceled due to lack of funding. In 1995 the exact same project was funded and the project went ahead. Assume you have gone on to work on other projects. You are aware that in the 1993 edition of this handbook a number of revisions were made, one requiring fusing and circuit breakers to use the next lower, or rounding down, of the fuse and circuit breaker sizes. What action, if any, should you take? The client for the project is that firm that produces molded rubber parts. They have a project manager overseeing the plant design. Call this project manager and tell him of the needed change in fuse rating to match the present electrical code Call the electrical engineer you know is working on the project reminding him that the prior work was based on the code in force in 1991 and not the latest code. gnore the project since you are working in another area now Write a memo to the project supervisor of the change in the code and the need to revise the fuse rating.

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